Exciting-dynamo.



Patented Oct. 28, I902.

H. W. BUCK.

EXCITING DYNAIO.

(Application and hpt. a, 1808.)

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H. W. BUCK.

EXCITING DYNAIO (Applicltion filed Sept. 2, 1390.

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\A/l plzsszs. 'I h/ HB- 4 Harold W. uck, M KW- y UNITED STATES PATENTOFFICE.

HAROLD W. BUCK, OF SCIIENECTADY, NEW YORK, ASSIGNOR TO THE GENERALELECTRIC COMPANY, A CORPORATION OF NEYV YORK.

EXClTlNG-DYNAMO.

SPECIFICATION forming part of Letters Patent N 0. 712,041, dated October28, 1902. Application filed September 2. 1898. Serial llo. 690,133. (Nomodel.)

To all whom it may concern.-

Be it known that I, HAROLD W. BUCK, a citizen of the United States,residing at Schenectady, county of Schenectady, State of New York, haveinvented certain new and useful Improvements in Exciting-Dynamos, (CaseNo. 673,) of which the following is a specificat-ion.

My invention relates to means for exciting the fields of direct-currentdynamo-electric machines, and comprises a construction in which theusual field-magnet winding is entirely omitted and in which theexcitation is due to artificially-produced leading currents in the coilsof the armature or other winding movable relatively to the field-magnet.

In the drawings attached to this specification, Figures 1 to 5,inclusive, are illustrative diagrams. Fig. 6 represents diagrammaticallyan embodiment of my invention, and Fig. 7 a modification of the same.

Before proceeding to a description of my invention a few well-knownprinciples will be reviewed in order to make clearer the explanation tofollow.

In Fig. 1 let G represent a Gramme ring of the usual form, and M aninternal field-magnet energized from some external source of directcurrent. Let the armature be tapped at diametrically opposite points ab, so as to form an alternating-current generator, and assume thearmature to be rotated in the direction of the arrow, the currentgenerated being fed to a non-inductive load R. With this arrangement thecurrent will be approximately in phase with the impressed electromotiveforce, so that the maximum armaturecurrent will flow at the same timethat the armature electromotive force is a maximum. The relativeposition of armature and field corresponding to maximum armatureelectromotive force is shown in Fig. 1, in which the diameter a, b is atright angles to the field. In this position the armature and the fieldmagnetomotive forces are at right angles to each other, so that there isno component of either magnetomotive force in the direction of theother. The armature-current will therefore neither magnetize nordemagnetize the field by its reaction thereon. The only effect is one ofdistortion. Suppose, however, that the generator feeds a load havingcapacity reactancesuch as a condenser K, Fig. 2. In this case thecurrent will not be in phase with the electromotive force producing it,but will lead by an angle equal approximately to ninety degrees orone-quarter of a period. In this case, therefore, the armature-currentwill reach its maximum one-quarter of a period earlier than if the loadwere non-reactive, as in Fig. 1, and the armature-terminals a b willconsequently occupy a position displaced or trailed backward ninetydegrees when the maximum value of current occurs, as illustrated in Fig.2. By making the armature-current leading it reaches its maximumearlier, and its magnetomotive force has a component in the samedirection as the field-exciting magnetomotive force, and so assists thelatter. As the armature rotates to the position shown in Fig. 3 thearmature-current becomes zero, at which time there is no magnetizingreaction on the field. One-quarter of a revolution later, as shown inFig. 4., the condensercurrent again becomes a maximum and the field isreacted upon and magnetized in the same direction as in Fig. 2. Twiceevery revolution, therefore, the field will be magnetized by thereaction of the leading armature current, thus producing a pulsatingflux of a frequency depending on the rate of rotation of the armature.If, however, as shown in Fig. 5, the condensers be connected at regularintervals about the armature-wind ing, so as to be in multiphaserelation thereto, there will be a practically constant reactivemagnetization of the field by the leading condenser-currents in thearmature. The. external magnetization of the field may consequently beremoved and thesystem will excite itself by the reaction of the wattlessleading currents in the armature.

Having thus reviewed the principles underlying my invention, I will nowproceed to a description of the same as embodied in a direct-currentdynamo-electric machine.

In Fig. (5, G is a suitable armature. (Here shown as a Gramme ring.) Atequal spaces about the armature connections are tapped off to acorresponding number of sources of I00 leading electromotive force 0 OC. These may be either condensers, electrolytic cells, oroverexcitedsynchronous motors. A commutator K is connected to the armature in theusual way, with brushes B. B bearing thereon. An unwound field-magnet Vis in inductive relation to the armature and is here shown as internallyarranged with respect to the same. As has been seen, the reaction of theleading currents flowing in the condensers will magnetize the field andthe field thus established will generate a direct current, which may betaken from the commutator by the brushes B B, as in other direct-currentmachines. The leading currents will continue to flow in the armatureindependent of whatever load-current may be taken from the commutator.In a machine of the character described the field strength depends uponthe current flowing into the condensers, so that the field strength, andconsequently the voltage of the machine, may be varied by varying thecondenser capacity in any suitable manner.

The mechanical construction of a machine such as described may undergomany modifications and its principle may be embodied in many diiferenttypes of machines without departing from the spirit of my invention.Thus the field-magnets may be either internal, as shown in Fig. 6, andwithout windings thereon, or they may be external, with shortprojections forming the pole-pieces. In the latter case the poles areshort and the mag netic circuits compact, because no necessity existsfor providing space for winding fieldcoils.

In Fig. 7 of the drawings I have shown diagrammatically an arrangementof apparatus similar to that shown in Fig. 6, but comprising in additionmeans whereby the capacity or condenser eiTect may be convenientlyvaried, and thereby vary the direct-current electromotive force.Referring to Fig. 7, V represents an unwound field-magnet, eitherstationary or capable of rotation. In inductive relation thereto is arelatively rotatable armature G, having any suitable Winding, which inthe instance shown is of the Gramme type. This winding is tapped atintervals and connected to the segments of a commutator K in a mannercommon to direct-current machines. Brushes B B bear on the commutatorand serve to collect and transmit the current generated to the externalcircuit. The armature-winding is tapped at suitable intervals andconnections led off through collector-rings or by other appropriatemeans to the primary of a transformer. In the case shown in the drawingsthe armature-winding is tapped at three equidistant points, so as toproduce electromotive forces displaced in phase from each other by onehundred and twenty degrees. The transformer required is therefore of thethree-phase type. Although in the form shown the transformerwindings,both primary and secondary, have a Y connection, it is obvious that thedelta connection may be employed in either primary or secondary, orboth, as may be desired. A condenser C is connected to the secondary ofthis transformer and is of the three-phase type, in which three sets ofplates are connected, respectively, to the threephase mains, while theremaining sets of plates are connected to a common point, or, whatamounts to the same thing, in parallel. This condenser is connected withthe secondary of the transformer by conductors connecting, respectively,with the switch-arms 7, 8, and 9, as shown. Each switch-arm cooperateswith a plurality of contacts 11,in electrical connection with points inthe windin g of each leg of the transformer. By shifting theswitch-armsfrom one set of contactpoints to another the ratio of transformation ofthe tronsformer, and consequently its secondary voltage, is changed. Byso doing the capacity eifect in the primary due to the condenser in thesecondary is varied in a manner well understood by engineers, therebyvarying the volume of leading currents in the winding of the armature G.The field excitation varies in accordance with the variation of leadingcurrents, and thus regulates and determines the desired current andvoltage of the machine. The switch-arms 7, 8, and 9 may be operatedindependently, if desired; but I find it more convenient to connect themtogether by a connecting-rod 10, so as to secure a simultaneous movementof the same. The employment of a transformer in the manner described hasseveral advantages. If the windings be such that the ratio oftransformation is greater than one, or, in other words, if the secondaryvoltage be greater than the primary, I mayemploy a much smaller and lessexpensive condenser than would be required if the condenser wereconnected direct to the armature-winding, as shown in Fig. 5. By varyingthe ratio of transformation in the manner described the capacity efiectmay be varied more conveniently and through smaller gradations thancould be easily attained merely by the use of a condenser the capacityof which is variable step by step in the usual way.

In general, the construction of a machine embodying my invention wouldbe somewhat similar to that of a rotary converter, one side of thearmature being connected to a commutator in the usual manner and theother side of the armature tapped at regular intervals and connected tocollector-rings, which in turn are connected to condensers or otherappropriate sources of leading electromotive force.

Although the invention, as illustrated in Figs. 6 and 7, is shown asapplied to a bipolar Gramme-ring construction, it is obvious that itisequally applicable to machines of any number of poles and with any typeof armature or armature-Winding. Consequently I do not limit myself tothe exact forms shown in the drawings, either as to the number of poles,styles of winding, or number of phases used on the condenser-circuit.

What I claim as new, and desire to secure by Letters Patent of theUnited States, is-

1. In a direct-current dynamo-electric machine, an unwound field-magnet,a winding in inductive relation to the field-magnet and means forpassing leading currents through said winding.

2. A direct-current dynamo-electric machine having an armature and anunwound field-magnet, and means for advancing the phase of the currentsin the armature-windmg.

3. The combination of a direct-current dynamo-electric machine having aclosed-coil armature, and means for causing leading currents to flow inthe armature-Winding.

4. The combination of adirect-current dynamo-electric machine, and meansfor exciting one member of the machine by wattless current flowing inthe other.

5. The combination of a direct-current dynamo-electric machine, andcondensers in multiphase relation to the armature-winding.

6. The combination in a dynamo-electric machine, of a field-magnet, awinding movable relatively to the field-magnet and means for acting onthe winding by a plurality of leading electromotive forces in multiphaserelation to each other.

7. The combination of a direct-current dynamo-electric machine, andmeans for acting upon the field-magnets of the machine by magnetomotiveforces due to wattless currents.

S. The combination of a direct-current dynamo-electric machine having aclosed-coil armature, and means for causing phase-displaced currents tofiow in the armature-winding.

9. The combination of a direct-current dynamo-electric machine, anauxiliary alternating-current circuit having its terminals connected tothe armature-winding and containing means for adjusting the phaserelation between the current and the electromotive force in the armaturecircuit or circuits.

10. The combination of a direct-current dynamo-electric machine, aplurality of out-ofphase alternating-current circuits suitably connectedto the armature-winding and containing means for adjusting the phaserelation between current and electromotive force in the armature circuitor circuits.

11. The combination of a direct-current dynamo-electric machine, aplurality of auxiliary circuits the terminals of which are so connectedto the armature-winding as to receive out-of-phase currents therefrom,and means included in said circuits for adjusting the phase relationbetween current and electromotive force in the armature circuit orcircuits.

In testimony whereof I have hereunto set my hand this 31st day ofAugust, 1898.

HAROLD W. BUCK.

Witnesses:

A. F. MACDONALD, A. H. ABELL.

